The resting potential is a nerve
cell's (or neuron's) state of electropotential charge when it is in
a state of rest ready to receive a nerve impulse (the action
potential). The resting potential is a state of disequillibrium where
the surrounding extracellular fluid has a positive charge and the neuron
itself has a negative charge. The charge difference is created by positively
charged particles (potassium and sodium ions)
outside the cell which are kept apart from negatively charged particles
(chlorine and protein ions) by a semi-permeable membrane. Special selective
gates in the membrane called
Sodium and
Potassium Channels let through sodium
and potassium ions respectively when they are open. The channels open and
close in response to electrical or chemical stimuli.

How the resting potential potential is maintained and
how it works in respect to nerve impulses is discussed more fully in the
section on the action potential.